Roca et al 2001

Vilgalys

6

Brown et al. 1999

Decrease in Age of Island Movement of Pacific plate

Mendelson and Shaw 2005

Distinquishing within- vs. between-island speciation using evolutionary trees Within-island speciation

Distinquishing within- vs. between-island speciation using evolutionary trees Between-island speciation

Geographic (island) distribution Parsimony reconstruction

Host association in Trupanea arboreae Dubautia arborea Dubautia scabra Dubautia ciliolata Dubautia linearis Argyroxiphium kauense

Darwin: geographic separation followed by gradual (slow) adaptation to different ecological circumstances eventually leads to reproductive isolation Two alternatives allow rapid speciation: –FOOD: Speciation due to shifts in host -- without geographic isolation –SEX: Speciation due to divergent sexual selection - with brief geographic isolation Mechanisms of species formation

Model of sympatric speciation via shifts to new host (FOOD) 1 Population uses ancestral host Host shift New population founded via shift to derived host 2 Populations on two hosts become reproductively isolated

Signatures of sympatric speciation via host/habitat shift (after Via 2001) Sympatric overlap of host patches Mating on the host causes reproductive isolation between races Host phenology differs Divergent selection on different hosts/habitats

Illustration from Abrahamson and Weis (1997) Goldenrod gallmaker -- Eurosta solidaginis – an example of speciation via host-plant shift Photo:Warren Abrahamson

Speciation via SEXual selection Females in ancestral populations prefer blue males Geographic barrier divides populations Female preference for male trait diverges due to genetic drift Upon recontact, populations reproductively isolated due ONLY to female preference

Signatures of speciation via sexual selection (after Panhuis et al. 2001) Populations within species vary in sexually selected traits and associated preferences, resulting in partial pre-mating isolation Closely related species differ markedly in mating signals and preferences, which constitute the primary barrier to gene exchange Species differ in few other traits besides those involved in mate choice

from Turgeon et al North American Enallagma

Turgeon et al. 2005

Damselfly Mating Practices Photo: Denise Steele, Dartmouth College

McPeek et al. (in press)

Robertson and Paterson, Evolution.

McPeek et al. (in press)

Shape evolution NS different from “punctuated evolution”

McPeek et al Change in female shape correlated to change in male shape

Brown, McPeek and May.2000 Syst. Biol. 49:

Selection and the Enallagma radiation Four damselfly-lake species generated by habitat shifts and adaptive evolution (morphological, behavioral and physiological) Many fish-lake species generated during recent radiations (associated with glacial retreat?), possibly via founder effects on mechanical mate recognition system

Shaw and Lesnick 2009